How is a Minigrid defined?
I recently attended the Affordable Energy for Humanity Workshop in Potsdam and was surprised: Many experts on rural electrification attended the workshop, and everyone including myself had a different definition and understanding of a Minigrid and what it entails. Although we agreed on some common elements, we did not establish a common definition.
Now, the question “How is a Minigrid defined?” may seem very easily be answered: It is a small grid. But is this sufficient? Do we really know, what is meant by the term “Minigrid” if we say it is a smaller version of the interconnected grids we know from developed countries?
I don’t think we do . Especially not, when other terms, such as Microgrids, also hover around the space. What is the difference between a Minigrid and a Microgrid? Some people use the terms interchangeable, others say the one is the smaller version of the other – with sometimes Microgrids being larger, and sometimes Minigrids. Interestingly enough, Minigrids have been around since the 1980’s and yet, there seems to be no clear definition of the term itself.
Sometimes publications state their own definitions, such as for example the Minigrid Policy Toolkit issued by RECP, EUEI PDF, ARE and REN 21, where a Minigrid is defined the following:
In this publication we define mini-grids as involving small-scale electricity generation (from 10kW to 10MW), and the distribution of electricity to a limited number of customers via a distribution grid that can operate in isolation from national electricity transmission networks and supply relatively concentrated settlements with electricity at grid quality level. “Micro-grids” are similar to mini-grids but operate at a smaller size and generation capacity (1-10 kW).
Does size matter?
Similar like the definition above, a lot of the definitions refer to size of the system, but I believe this excludes possible systems, that still fall within the same category. For example, if a Minigrid has 9 kW – is it not a Minigrid anymore? What about one that has 11 MW installed capacity? Does this change what the purpose of the grid actually was? How to deal with systems that were started at 9 kW and grew maybe to some hundred kW? Are these suddenly a different type? I don’t think that this is the case.
Typical Minigrid features
So what to do about it? In my belief, the definition has to be independent of size, but rather by functionality. So, what are key aspects to consider, when dealing with a Minigrid?
- Minigrids include generation assets
- Minigrids include a distribution grid
- Minigrids include a metering & payment infrastructure (Note: payment could even be manual)
- Minigrids can have, but not mandatory have, renewable energy sources
- Minigrids can supply energy for some hours, or 24/7
- Minigrids supply always at least 2 households (if only 1 – it is a solar home system)
- Minigrids purpose is to provide electrical energy to customers that had no electrical energy access before
- Minigrids can be technology open, e.g. not necessarily have to be AC based, but can be DC based
- Minigrids can have storage technologies, but not necessarily have them
- Once it is connected to the main grid, it becomes an element of this.
My Minigrid definition
Based on the criteria, I came up with a definition, that I believe is most accurately, while keeping it flexible on the size matter.
A Minigrid is a power system built up in either AC or DC technology, with the purpose to provide electrical energy access in areas without access to an interconnected grid to 1+n (with n>=1) customers and may include any possible combination of non-renewable and renewable power generation assets, the power distribution assets, possible energy storage assets as well as a metering and payment infrastructure, offering each connection a pre-defined time and type of energy supply and respective tariff, that may or may not be integrated to the main grid in the future.
Do you think my definition is good enough to cover all Minigrids? Is it missing an important element I didn’t think of?
Of course, now the question remains: How does a Microgrid differ from this? More on this in my next blog post!